1/*
  2 * gpio-event-mon - monitor GPIO line events from userspace
  3 *
  4 * Copyright (C) 2016 Linus Walleij
  5 *
  6 * This program is free software; you can redistribute it and/or modify it
  7 * under the terms of the GNU General Public License version 2 as published by
  8 * the Free Software Foundation.
  9 *
 10 * Usage:
 11 *	gpio-event-mon -n <device-name> -o <offset>
 12 */
 13
 14#include <unistd.h>
 15#include <stdlib.h>
 16#include <stdbool.h>
 17#include <stdint.h>
 18#include <stdio.h>
 19#include <dirent.h>
 20#include <errno.h>
 21#include <string.h>
 22#include <poll.h>
 23#include <fcntl.h>
 24#include <getopt.h>
 25#include <inttypes.h>
 26#include <sys/ioctl.h>
 27#include <sys/types.h>
 28#include <linux/gpio.h>
 29
 30int monitor_device(const char *device_name,
 31		   unsigned int line,
 32		   uint32_t handleflags,
 33		   uint32_t eventflags,
 34		   unsigned int loops)
 35{
 36	struct gpioevent_request req;
 37	struct gpiohandle_data data;
 38	char *chrdev_name;
 39	int fd;
 40	int ret;
 41	int i = 0;
 42
 43	ret = asprintf(&chrdev_name, "/dev/%s", device_name);
 44	if (ret < 0)
 45		return -ENOMEM;
 46
 47	fd = open(chrdev_name, 0);
 48	if (fd == -1) {
 49		ret = -errno;
 50		fprintf(stderr, "Failed to open %s\n", chrdev_name);
 51		goto exit_close_error;
 52	}
 53
 54	req.lineoffset = line;
 55	req.handleflags = handleflags;
 56	req.eventflags = eventflags;
 57	strcpy(req.consumer_label, "gpio-event-mon");
 58
 59	ret = ioctl(fd, GPIO_GET_LINEEVENT_IOCTL, &req);
 60	if (ret == -1) {
 61		ret = -errno;
 62		fprintf(stderr, "Failed to issue GET EVENT "
 63			"IOCTL (%d)\n",
 64			ret);
 65		goto exit_close_error;
 66	}
 67
 68	/* Read initial states */
 69	ret = ioctl(req.fd, GPIOHANDLE_GET_LINE_VALUES_IOCTL, &data);
 70	if (ret == -1) {
 71		ret = -errno;
 72		fprintf(stderr, "Failed to issue GPIOHANDLE GET LINE "
 73			"VALUES IOCTL (%d)\n",
 74			ret);
 75		goto exit_close_error;
 76	}
 77
 78	fprintf(stdout, "Monitoring line %d on %s\n", line, device_name);
 79	fprintf(stdout, "Initial line value: %d\n", data.values[0]);
 80
 81	while (1) {
 82		struct gpioevent_data event;
 83
 84		ret = read(req.fd, &event, sizeof(event));
 85		if (ret == -1) {
 86			if (errno == -EAGAIN) {
 87				fprintf(stderr, "nothing available\n");
 88				continue;
 89			} else {
 90				ret = -errno;
 91				fprintf(stderr, "Failed to read event (%d)\n",
 92					ret);
 93				break;
 94			}
 95		}
 96
 97		if (ret != sizeof(event)) {
 98			fprintf(stderr, "Reading event failed\n");
 99			ret = -EIO;
100			break;
101		}
102		fprintf(stdout, "GPIO EVENT %llu: ", event.timestamp);
103		switch (event.id) {
104		case GPIOEVENT_EVENT_RISING_EDGE:
105			fprintf(stdout, "rising edge");
106			break;
107		case GPIOEVENT_EVENT_FALLING_EDGE:
108			fprintf(stdout, "falling edge");
109			break;
110		default:
111			fprintf(stdout, "unknown event");
112		}
113		fprintf(stdout, "\n");
114
115		i++;
116		if (i == loops)
117			break;
118	}
119
120exit_close_error:
121	if (close(fd) == -1)
122		perror("Failed to close GPIO character device file");
123	free(chrdev_name);
124	return ret;
125}
126
127void print_usage(void)
128{
129	fprintf(stderr, "Usage: gpio-event-mon [options]...\n"
130		"Listen to events on GPIO lines, 0->1 1->0\n"
131		"  -n <name>  Listen on GPIOs on a named device (must be stated)\n"
132		"  -o <n>     Offset to monitor\n"
133		"  -d         Set line as open drain\n"
134		"  -s         Set line as open source\n"
135		"  -r         Listen for rising edges\n"
136		"  -f         Listen for falling edges\n"
137		" [-c <n>]    Do <n> loops (optional, infinite loop if not stated)\n"
138		"  -?         This helptext\n"
139		"\n"
140		"Example:\n"
141		"gpio-event-mon -n gpiochip0 -o 4 -r -f\n"
142	);
143}
144
145int main(int argc, char **argv)
146{
147	const char *device_name = NULL;
148	unsigned int line = -1;
149	unsigned int loops = 0;
150	uint32_t handleflags = GPIOHANDLE_REQUEST_INPUT;
151	uint32_t eventflags = 0;
152	int c;
153
154	while ((c = getopt(argc, argv, "c:n:o:dsrf?")) != -1) {
155		switch (c) {
156		case 'c':
157			loops = strtoul(optarg, NULL, 10);
158			break;
159		case 'n':
160			device_name = optarg;
161			break;
162		case 'o':
163			line = strtoul(optarg, NULL, 10);
164			break;
165		case 'd':
166			handleflags |= GPIOHANDLE_REQUEST_OPEN_DRAIN;
167			break;
168		case 's':
169			handleflags |= GPIOHANDLE_REQUEST_OPEN_SOURCE;
170			break;
171		case 'r':
172			eventflags |= GPIOEVENT_REQUEST_RISING_EDGE;
173			break;
174		case 'f':
175			eventflags |= GPIOEVENT_REQUEST_FALLING_EDGE;
176			break;
177		case '?':
178			print_usage();
179			return -1;
180		}
181	}
182
183	if (!device_name || line == -1) {
184		print_usage();
185		return -1;
186	}
187	if (!eventflags) {
188		printf("No flags specified, listening on both rising and "
189		       "falling edges\n");
190		eventflags = GPIOEVENT_REQUEST_BOTH_EDGES;
191	}
192	return monitor_device(device_name, line, handleflags,
193			      eventflags, loops);
194}